/*
 * Copyright � 2002-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System.Collections;
using System.Collections.Specialized;
using Spring.Util;

namespace Spring.Core.TypeResolution;

/// <summary>
/// Resolves (instantiates) a <see cref="System.Type"/> by it's (possibly
/// assembly qualified) name, and caches the <see cref="System.Type"/>
/// instance against the type name.
/// </summary>
/// <author>Rick Evans</author>
/// <author>Bruno Baia</author>
/// <author>Erich Eichinger</author>
public class CachedTypeResolver : ITypeResolver
{
    /// <summary>
    /// The cache, mapping type names (<see cref="System.String"/> instances) against
    /// <see cref="System.Type"/> instances.
    /// </summary>
    private IDictionary typeCache = new HybridDictionary();

    private ITypeResolver typeResolver;

    /// <summary>
    /// Creates a new instance of the <see cref="Spring.Core.TypeResolution.CachedTypeResolver"/> class.
    /// </summary>
    /// <param name="typeResolver">
    /// The <see cref="Spring.Core.TypeResolution.ITypeResolver"/> that this instance will delegate
    /// actual <see cref="System.Type"/> resolution to if a <see cref="System.Type"/>
    /// cannot be found in this instance's <see cref="System.Type"/> cache.
    /// </param>
    /// <exception cref="System.ArgumentNullException">
    /// If the supplied <paramref name="typeResolver"/> is <see langword="null"/>.
    /// </exception>
    public CachedTypeResolver(ITypeResolver typeResolver)
    {
        AssertUtils.ArgumentNotNull(typeResolver, "typeResolver");
        this.typeResolver = typeResolver;
    }

    /// <summary>
    /// Resolves the supplied <paramref name="typeName"/> to a
    /// <see cref="System.Type"/>
    /// instance.
    /// </summary>
    /// <param name="typeName">
    /// The (possibly partially assembly qualified) name of a
    /// <see cref="System.Type"/>.
    /// </param>
    /// <returns>
    /// A resolved <see cref="System.Type"/> instance.
    /// </returns>
    /// <exception cref="System.TypeLoadException">
    /// If the supplied <paramref name="typeName"/> could not be resolved
    /// to a <see cref="System.Type"/>.
    /// </exception>
    public Type Resolve(string typeName)
    {
        if (StringUtils.IsNullOrEmpty(typeName))
        {
            throw BuildTypeLoadException(typeName);
        }

        Type type = null;
        try
        {
            lock (this.typeCache.SyncRoot)
            {
                type = this.typeCache[typeName] as Type;
                if (type == null)
                {
                    type = this.typeResolver.Resolve(typeName);
                    this.typeCache[typeName] = type;
                }
            }
        }
        catch (Exception ex)
        {
            if (ex is TypeLoadException)
            {
                throw;
            }

            throw BuildTypeLoadException(typeName, ex);
        }

        return type;
    }

    private static TypeLoadException BuildTypeLoadException(string typeName)
    {
        return new TypeLoadException("Could not load type from string value '" + typeName + "'.");
    }

    private static TypeLoadException BuildTypeLoadException(string typeName, Exception ex)
    {
        return new TypeLoadException("Could not load type from string value '" + typeName + "'.", ex);
    }
}
